Fastmail MCP Server (Unofficial)

An unofficial MCP (Model Context Protocol) server that provides access to Fastmail email via effect-jmap.

Connect to a client

Claude Desktop

claude mcp add fastmail --env FASTMAIL_API_TOKEN=<YOUR_TOKEN> npx fastmail-mcp-unofficial

Or manually add this to your Claude Desktop configuration:

{
  "mcpServers": {
    "fastmail": {
      "command": "npx",
      "args": ["fastmail-mcp-unofficial"],
      "env": {
        "FASTMAIL_API_TOKEN": "your_token_here"
      }
    }
  }
}

Tools

This MCP server provides the following tools:

mailbox_get

Retrieves all mailboxes from the account.

• No parameters required
• Returns array of mailbox objects with metadata

email_get

Gets specific emails by their IDs.

• emailIds (required): Array of email IDs to retrieve
• accountId (optional): Account ID to retrieve emails from (auto-detected if not provided)
• properties (optional): Specific properties to fetch
• fetchTextBodyValues (optional): Fetch text/plain body values
• fetchHTMLBodyValues (optional): Fetch text/html body values
• fetchAllBodyValues (optional): Fetch all text body values
• maxBodyValueBytes (optional): Maximum size in bytes for body values

email_query

Queries emails with filters and sorting.

• mailboxId (optional): Mailbox ID to search in
• limit (optional, default: 10): Maximum number of emails to return
• from (optional): Filter by sender
• to (optional): Filter by recipient
• subject (optional): Filter by subject text
• hasKeyword (optional): Filter by keyword (e.g., '$seen', '$flagged')
• notKeyword (optional): Filter by absence of keyword
• before (optional): Filter by date (ISO format)
• after (optional): Filter by date (ISO format)
• sort (optional, default: 'receivedAt'): Sort by property
• ascending (optional, default: false): Sort order

Development

• pnpm dev - Watch mode for TypeScript compilation
• pnpm typecheck - Type check without emitting files
• pnpm build - Build for production

Getting Your Fastmail API Token

The server requires a Fastmail API token to be provided via the MCP client configuration (see above).

To create your API token:

1. Go to Fastmail Settings
2. Navigate to Privacy & Security
3. Under "Connected apps & API tokens", click "Manage API tokens"
4. Create a new API token with appropriate permissions

The JMAP session endpoint is hardcoded to https://api.fastmail.com/jmap/session.